The conventional method of clamping the saddle post in the bicycle frame downtube is to split the down tube at the top for several inches, then placing a clamp around the tube which has a through bolt which when tightened, compresses the split down tube against the saddle post to retain it.
Often the clamping action is accomplished by two bosses welded to the opposite sides of the slot. The clamp bolt passes through the two bosses.
Often the clamping action is accomplished by a camming lever as illustrated in Hon's patent U.S. Pat. No. 4,067,586, sheet 4, FIG. 10.
In my patent U.S. Pat. No. 4,872,696, I use a folded over center toggle mechanism to produce the required clamping force which can amount to 2 to 3 thousand pounds. It is the saddle post maximum load divided by the metal to metal friction coefficient of the area under the clamp.
Baucher, U.S. Pat. No. 3,848,008, and Newlands, U.S. Pat. No. 4,120,512, cited in my patent, are bolt actuated variations without the usual bosses and cannot be quickly loosened or tightened.
Of the quick adjusting saddle patents, that of Girardt Fils (French 578,011) consists of a sliding bolt in the bicycle horizontal frame tube engaging a series of notches in the saddle post, the bolt being engaged in the notches by a spring and released by a chain extending to the handlebars, where it is pulled by a lever.
Weinzierl (German 28 24 974) employs a sliding horizontal plate to engage notches in the seat post. The plate is moved by a cable actuated bellcrank.
Walters, in (U.K. Patent 2,116128) discloses a similar horizontal bolt entering a series of holes in the saddle post tube into which the bolt is moved by a means not shown. A spring within the downtube urges the post upward when there is no weight on the saddle.
Cienfuegos (U.S. Pat. Nos. 4,150,851 and 5,044,592) uses a similar horizontal spring loaded bolt engaging holes in the saddle post.
Cardon (Fr. 470,907) also uses a spring loaded bolt engaging holes in the saddle post.
All these embodiments produce stepwise movement, limited by the spacing of the slots or holes, also the saddle post tube must be positioned within about one half of the slot or hole diameter, otherwise the bolt will not enter fully. If the bolt is not entered fully, a not easily checked condition when the rider sits down, the bolt may slip, giving a disconcerting jounce to the rider. This could be hazardous in a turn at high speed.
Cutting the numerous slots or holes can be expensive as they must be burr free to operate properly.
Tajima, U.S. Pat. No. 3,861,740, discloses a hydraulically operated oil cylinder which is forced upward by a compressed gas chamber. The operation is controlled by a small oil valve controlled by a cable to the handlebar.
This embodiment produces the desired action for the saddle post, but it is complicated, expensive, and subject to oil leakage.
Phillips (G.B. 703,798) discloses a vertical slot formed in the body of the seat post, in which a double lobed cam is rotated. When the cam is rotated, it expands the seatpost to frictionally engage the interior of the frame downtube. Infinitely variable positions are available, but the price is a specially formed saddle post as well as the mounting of the cam mechanism on the bicycle frame. Also sufficient force must be exerted in rotating the cam to expand the saddle post tube as well as developing adequate frictional drag to prevent movement of the saddle post in the down tube.